The structure of the thermal equilibrium state of a weakly interacting Bose gas is of current interest. We calculate the density matrix of that state in two ways. The most effective method, in terms of yielding a simple, explicit answer, is to construct a generating function within the traditional framework of quantum statistical mechanics. The alternative method, arguably more interesting, is to construct the thermal state as a vector state in an artificial system with twice as many degrees of freedom. (...) It is well known that this construction has an actual physical realization in the quantum thermodynamics of black holes, where the added degrees of freedom correspond to the second sheet of the Kruskal manifold and the thermal vector state is a state of the Unruh or the Hartle–Hawking type. What is unusual about the present work is that the Bogolubov transformation used to construct the thermal state combines in a rather symmetrical way with Bogolubov's original transformation of the same form, used to implement the interaction of the nonideal gas in linear approximation. In addition to providing a density matrix, the method makes it possible to calculate efficiently certain expectation values directly in terms of the thermal vector state of the doubled system. (shrink)

This book offers an introduction to the Sophists of fifth-century Athens and a new overall interpretation of their thought. Since Plato first animadverted on their activities, the Sophists have commonly been presented as little better than intellectual mountebanks - a picture which Professor Kerferd forcefully challenges here. Interpreting the evidence with care, he shows them to have been part of an exciting and historically crucial intellectual movement. At the centre of their teaching was a form of relativism, most famously expressed (...) by Protagoras as 'Man is the measure of all things', and which they developed in a wide range of views - on knowledge and argument, virtue, government, society, and the gods. On all these subjects the Sophists did far more than simply provoke Plato to thought. Their contributions were substantial and serious; they inaugurated the debate on many central philosophical questions and decisively shifted the focus of philosophical attention from the cosmos to man. (shrink)

Do we remember what pain feels like? Investigations into this question have sometimes led to ambiguous or apparently contradictory results. Building on research on pain memory by Rohini Terry and colleagues, I argue that this lack of agreement may be due in part to the difficulty researchers face when trying to convey to their study's participants the type of memory they are being tasked with recalling. To address this difficulty, I introduce the concept of 'qualitative memory', which, arguably, is the (...) sort of memory we have of what red looks like yet lack with respect to pain. I also briefly address a number of consequences the acknowledgment of qualitative memory would potentially have for philosophy, arguing that if we fail to have qualitative memories of certain sensations, such as pain, the standard philosophical accounts of experience, rational choice, and the sources of moral action may all need revision. (shrink)

An implication is a proposition, a consequence is a relation between propositions, and an inference is act of passage from certain premise-judgements to another conclusion-judgement: a proposition is true, a consequence holds, whereas an inference is valid. The paper examines interrelations, differences, refinements and linguistic renderings of these notions, as well as their history. The truth of propositions, respectively the holding of consequences, are treated constructively in terms of verification-objects. The validity of an inference is elucidated in terms of the (...) existence of a chain of immediately evident steps linking premises and conclusion. (shrink)

Susan Schneider argues that physicalism must be false if abstracta are part of the physicalist's dependence base. In opposition to her view, here I set out some reasons to think that abstracta in general, including abstracta that are woven into the dependence base, are something physicalists can countenance with consistency.

This chapter contains sections titled: I II III IV V VI VII VIII IX X.

There is great skepticism about the admittance of expert normative ethics testimony into evidence. However, a practical analysis of the way ethics testimony has been used in courts of law reveals that the skeptical position is itself based on assumptions that are controversial. We argue for an alternative way to understand such expert testimony. This alternative understanding is based on the practice of clinical ethics.

The problem of finding irreducible representations of a simple Lie group that decompose into just pure replications of a representation of a subgroup is considered. Replications involving tensor representations of the orthogonal groups are studied in detail using counting groups whose representation dimensions correspond to branching multiplicities. Replications involving spinor and mixed tensor representations are briefly considered.

The original Feynman-Wheeler perfect absorber theory lead to the Instantaneous Action at a Distance formulation. We observe that this is perfectly meaningful in the light of recent studies pointing to a small but non-zero photon mass. The Quantum Mechanical effects within the Compton scale of such a small mass photon would lead to the above formulation.

The Special Theory of Relativity and the Theory of the Electron have had an interesting history together. Originally the electron was studied in a non-relativistic context and this opened up the interesting possibility that lead to the conclusion that the mass of the electron could be thought of entirely in electromagnetic terms without introducing inertial considerations. However the application of Special Relativity lead to several problems, both for an extended electron and the point electron. These inconsistencies have, contrary to popular (...) belief not been resolved satisfactorily to date, even within the context of Quantum Theory. Thus they are not merely of historical interest. Nevertheless these and subsequent studies bring out the interesting result that Special Relativity (and the theory of the electron) breaks down within the Compton scale or when the Compton scale is not neglected. This again runs contrary to an uncritical notion that Special Relativity is valid for point particles. Furthermore, it is pointed out that experiments have been recently suggested to test these ideas. These considerations lead to a characterization of the Planck constant in classical terms. (shrink)